Furnace lining



Sept. 11, 1962 F. H. N. CARTER FURNACE LINING 2 Sheets-Sheet Filed Nov.2, 1959 6 Q IMM g INVENTOR F/?EDEE/ CK h'. M U k' 75? j ATTO Sept. 11,1962 F. H..N. CARTER FURNACE LINING 2 Sheets-Sheet 2 Filed Nov. 2, 1959jo 12 uni 21 INVENTOR FPEDE/?ICK f/.N. 654275? 3,053,237 FURNACE LININGFrederick H. N. Carter, New York, N.Y., assignor to Sunrod ManufacturingCorporation, New York, N.Y., a co'poraton of Delaware Filed Nov. 2,1959, Ser. No. %0,206 7 Claims. (CI. 122-6) This invention relates toelectrc arc steel furnaces and especially to a lining, such as a coveror -roof therefor, which will operate longer and more efficiently thancovers presently in use.

Removable covers for steel furnaces are lined on the underside withrefractory material put in place by casting or in the form of bricks.Building the lining from bricks is expensive, requiring care in shapingthe lining in a domed shape and in fastening 'the bricks to the cover.Such linings are apt to be heavy and, therefore, diflicult to move.

A refractory known in the art as a high alumina castable may be -used toform the r-efractory layer in the cover. lt may be prepared as a liquidand spread over the surface of the cover after inverting the same, muchas concrete is spread in a mold in constructing a floor. It is notnecessary to cast such -refractories in a domed shape. Cast refractoriesare subject to deep cracking or crazing in use, however, and thereby maybecome separated into a fairly large number of irregular chunks orsections. It is desirable to hold the cast refractory in such a mannerthat these chunks will not fall from the cover into the molten metal.

Cast refractories are subject to fairly rapid erosion due to the highradiant temperature to which they are exposed. The temperature inside asteel furnace is in the neighborhood of 3,000 F., which is close to thebreakdown temperature of the refractory lining of the cover. Cooling ofthe refractory layer is desirable, but excessive cooling spells a lossof power because what is taken out by the cooling medium must -besupplied by the arcs. Therefore, it is desirable to reduce radiant heattransfer to the cover by maintaining the surface of the refractory layerexposed to the molten metal at as high a temperature as possible withoutproducing speedy disintegration.

Attempts have been made to cool covers with cooling pipes through whichcoolant is circulated. If these pipes are placed between the refractorymaterial and the molten metal mass they absorb too much heat and cutdown the efficiency of the furnace. Such an arrangement protects therefractory but requires a high current supply.

If the cooling pipes are placed above or imbedded in the refractory, dueto the low conductivity thereof, they may be of little assistance to thebottom surface which is exposed to the high radiant heat from the arcsand mix contained in the bottom of the furnace.

The present invention has as an object the production of a cover whichincludes cooling pipes with heat conductivity studs imbedded in therefractory which mechanically support the refractory and cool thesurface thereof only enough to prevent disintegration without removingso much heat as to make it necessary to supply excess current to thearcs.

Another object is to make a self compensating refractory surface whichwill automatically assume a satisfactory balance between minimum powerloss at the arcs and long life for the refractory surface.

Another object is the provision of heat conducting studs which are solocated relative to the cooling pipes and the cast refractory that evenif deep cracks in the refractory occur the resulting chunks or sectionswill be held in place by the studs.

Another object is the provson of cooling studs which Patented Sept. 11,1962 will bind the refractory to the cooling pipes without the necessityof leaving spaces between individual cooling pipes for fastening meansextending from above the cooling pipes into the cast refractory.

A further object is to provide a relatively large area of contactbetween the refractory and the metal cooling coils and studs.

In tests cover sections constructed in accordance with the presentinvention have lasted three or four times as long as adjacentconventional cover sections and have done so without any increase inpower consumption at the arcs.

Objects and advantages other than those above set forth will *beapparent from the following description of a preferred embodiment of theinvention, when read in connection with the accompanying drawingsthereof.

In the drawings:

FIG. 1 is a diagrammatic view in vertical cross section of an electrcarc steel furnace;

FIG. 2 is a -detail enlarged view of the right hand side of the cover orroof shown in FIG. l;

FIG. 3 is an enlarged partial section through 3-3 of FIG. 2;

FIG. 4 is a transverse sectional view through the cooling tubes of FIG.2, showing the studs attached to the tubes and a layer of refractorymaterial;

FIG. 5 is a plan 'view of a portion of the tubes and studs of the coveror roof before the refractory material is applied thereto; and

FIG. 6 is a view similar to FIG. 5 showing another type or form of stud.

Looking at the figures, F is an electrc arc steel furnace; 1 is the bodythereof which is made of or at least lined with refractory material; 2and 3 are electrodes projecting downwardly through the roof or coverinto the interior of the furnace.

The present invention has to do with the design and Construction of theroof or cov er. The cover, as shown at C, consists of a supportingframework which includes a steel box member 5 adapted to rest on theupper wall 1 of the body of the furnace F. This frame member may be someother cross section such as a channel or I-beam. However, the boXConstruction shown in FIGS. 1 and 2 has been found satisfactory. Restingon the box section member 5 are a plurality of I-beams 6. These supportinverted short U-shaped members 7 which in turn support long invertedU-shaped members 8 arranged parallel to the I-beam member 6. Members 6,7 and 8 are all welded together as shown in FIG. 3.

Members 8 support the cooling tubes shown at 10. These are arranged sideby side to cover most of the area of the roof and as shown in FIGS. 1and 2, may be arranged vertically, one on top of the other around theopenings for the electrodes.

Due to the high temperatures involved, it is desirable to support thecooling tubes 1 1]` to allow for contraction and expansion. This isaccomplished by welding U-shaped straps shown at 11, to the upper sideof the tubes as the cover is arranged for furnace operation.Corresponding openings are furnished in the members 8, as shown at 12,which o-penings are designed to accommodate the straps 11 -so that theymay pass'freely through the openings. Each strap with the attached tubeis drawn snugly up against the member 8 by means of a Wedge 15, shown inFIGS. 2 and 3. In this manner the rows of cooling tubes are more or lessflexibly supported on the members 8. The vertically arranged tubesaround the openings for the electrodes may be supported on thehorizontal rows of tubes or by a suitable vertical support attached tothe members 8 or 6.

The design of the supporting members may be varied to accommodate theshape of the cover and the number of electrodes in use. It is necessarythat the -supporting structure be strong enough to hold the coolingtubes so that undue strain will not be put -upon them when the cover ismoved. At the same time sufficient flexibility should be provided sothat various parts of the cover may expand and contract under thetemperature changes.

Attached to the cooling tubes and depending therefrom when the cover isin use, are studs 20 which project downwardly from the tubes and aredisposed at an angle to the vertical plane through the axis of the tubeand preferably alternate studs project on alternate sides of thisvertical plane, as shown in FIGS. 2, 4, and 6. In the pattern shown inFIGS. 5 and 6, the base of the studs where they join the tubes may bethought of as being located on some of the squares of a checkerboard inrows running from left to right and columns from top to bottom. Eachtube has two rows of such an imaginary checkerboard. The basic patternfor the studs which is repeated over the whole area of the tubes (exceptthe edges and where tubes bend, where extra studs .are displaced oradded) contains sixteen squares or possible 'stud locations in `fourrows and four columns. If the rows are numbered from one to fourproceeding from the top down and the columns from one to four with thefirst column on the left, there is a stud located in row one, columnfour and slanted toward the top of the figure. A second stud, slantedtoward the bottom of the figure, is in row two, column three, a third,slanted toward the top in row three, column one, and a fourth, slantedtoward the bottom in row four, column two. The remaining twelve squaresare empty. This arrangement of studs is repeated like a wallpaperpattern over much of the watercooled surface which is forrned by thetubes. The pattern allows all studs in a given row to slant in the samedirection and those in adjacent rows to slant in opposite directions. Bythis construction an interlocking pattern is produced and yet all studscan be welded perpendicular to the surfaces of the circular tubes, as ismost clearly shown in FIG. 4. It is desirable to have the base of thestud where it jons the cooling pipe or tube, of a larger cross sectionthan the outer end of the stud, because the inner end of the studagainst the tube normally carries a higher heat flow than the outer endof the stud.

FIG. 5 shows studs which have a more or less rectangular cross sectionbut decreasing in cross sectional area from the tube to the outer end ofthe stud. FIG. 6 shows a slight modification wherein the studs have thesh-ape of truncated cones as shown at 21.

Studs 20 and 21 may be used in many different shapes and arrangementsbut should be designed and disposed in relation to the tubes and to eachother so that they will function efficiently to 'transfer heat from therefractory layer to the coolant at such a rate as to produce areasonably long life in the refractory without subtracting more heatthan is necessary from the arcs and the melt in the furnace. Also, thestuds should be arranged so to give the maximum mechanical support tothe layer of refractory. The disposition shown in FIGS. 4, 5 and 6 hasbeen found quite satisfactory and it can be seen -from FIG. 4 that theoverlapping studs produce a criss cross arrangement which serves well tosupport the refractory.

The surface of the studs 20 and 21 may have an irregular shape; forinstance, concentric ridges could be formed on the surface or a slightlybulbous or enlarged end could be used to further enhance the mechanicalsupporting function of the studs. However, the arrangement disclosed in`FIGS. 4, 5 and 6 operates efliciently and it produces an interlacedreinforcement which serves to hold together the refractory layer evenafter it is cracked in places due to the -severe service imposed -by thehigh temperatures.

With studs on the cooling tubes, the spacing between the tubes is notcritical because the studs overlap one another and overlap the space.between the tubes. The tubes may be spaced very close together becausethere is no need to imbed them all the way in the refractory. They canalso be spaced apart because the outer ends of the studs overlap eachother and distribute the cooling effort throughout the layer ofrefractory material.

The cover carries a layer of refractory material, as shown .at 30 inFIGS. 2 and 4, and a cast type of refractory is desirable for thepresent invention. In order to install or replace a refractory layer thecover is removed from the furnace and turned upside down. The castrefractory is then poured into place as one might pour cement into amould. It has been found that if the refractory is poured to a depth ofabout one inch above the outer ends of the studs, satisfactory operationwill be obtained. It has also been found that cast refractory such asthat known as high alumina castable can be used for the purpose of thisinvention. Such castable refractory `is supplied by the GeneralRefractories Co., under the name Special High Alumina Castable and bythe Babcock and Wilcox Co., under the name Kaocrete-32.

In renewing old refractory, it is found that after it has been subjectedto the heat of the furnace for some time and then the cover removed andturned upside down, it is a relatively sirnple matter to break out theold refractory and cast a new layer.

After the refractory has hardened, the cover is ready to be replaced onthe furnace and 'put to use.

In operation the studs serve to mechanically hold the refractory inplace and even though it may become cracked in use it is unlikely thatany substantial part of the refractory layer will actually drop ofi intothe mix.

The studs also serve along with the cooling tubes to cool the refractorylayer but the cooling tubes and studs do more than merely cool. Theyprovide a structure along 'with the refractory layer which automaticallymaintains the optimum temperature for the refractory layer. This optimumtemperature is a 'balance between too little cooling on one hand and toomuch on the other. If the layer is cooled too much, it absorbs thereflected heat from the arcs and the mix, which heat in turn must besupplied 'by the arcs with resulting inefficiency. If the refractorylayer is not cooled enough, it will break down, soften, crack and falloff into the mix which, of course, requires frequent renewal andconsequent shut downs of the furnace.

As a result, it is desirable to create :a condition where the refractorylayer will come to a state of equilibrium whereby it will withdraw aminimum of reflected heat from the interier of the furnace compatiblewith reasonably long life.

In the present construction, this is accomplished with the aid of thestuds attached to the cooling tubes which, as heretofore pointed out,serve the dual purpose of cooling the nterior of the refractory layerand mechanically supporting it. When the refractory layer is installed,it is made somewhat thicker than it will be after some little use in thefurnace. In operation when a new cover or a new layer of refractory isinstalled and the furnace brought up to temperature, the outer layer ofthe refractory will have a tendency to b'urn off and decrease the spacebetween the ends of the studs and the under surface of the refractory.As this space decreases, the cooling effect of the studs becomes greateron the lower surface of the refractory material and a balance is reachedwhereby the under surface of the refractory is cooled sufliciently bythe studs so that it is not readily burned away. Erosion will, ofcourse, continue at the very high temperature present but it will beslowed down to a point where the roof or cover will last three or fourtimes longer than conventional roofs or covers. A cover of this typeshould last three or four months and yet it will not absorb heat fromthe furnace in such quantity as to produce an ineficient operation. Inprior constructions the refractory layer broke down because ofinsuflicient cooling and, therefore, required frequent replacement, orwhere too much cooling was used, the efficiency of the furnace fell off.

In practice, water has been found to be a satisfactory coolant and itmay be put under pressure to discourage the generation of steam withinthe cooling parts. This practice is known in the art and is not a partof the present invention.

What is claimed is:

1. In a furnace lining comprising rows of interconnected cooling tubes,studs projecting from said tubes toward the interior of the furnace whenthe lining is in Operating position and a layer of refractory materialenclosing said studs and located between said tubes and the interior ofsaid furnace, the improvement wherein said studs are long enough and soslanted from a plane at right angles to the layer of refractory materialand passing through the longitudinal axis of the tube from which thestud projects as to overlap studs projecting in the opposite slantingdirection from an adjacent tube, when viewed in a plane at right anglesto the longitudinal axs of said tubes, to an extent so that the ends ofoverlapping studs project beyond each other and into the portions ofsaid layer of refractory material surrounding the overlapping studssufiiciently to lock said portions against sep aration from the rest ofsaid layer of refractory material.

2. The furnace lining of claim 1, wherein the studs join the surface inan overall pattern, characte'ized by a repetition of a basic pattern,said basic pattern being of rectangular Outline and having sixteenpossible stud positions arranged in four columns and four rows, the rowsbeing parallel to one side of the rectangular Outline and the columnsparallel to an adjacent side of the rectangular outline; the points ofattachment of the studs to the surface being located only as follows: afirst stud in the first row, fourth column; a second stud in the secondrow, third column; a third stud in the third row, first column; and afourth stud in the fourth row, second column; the axis of the studs of acolumn lying in an imaginary plane, said imaginary plane beingperpendicular to the surface and containing the column, the aXis of eachstud being slanted out of a direction perpendicular to the surface, thefirst and third toward one end of the column and the second and fourthtoward the other end of the column.

3. 'Ihe furnace lining of claim 1 wherein the studs join the tubes in anoverall pattern, characterized by a repetition of a basic pattern, saidbasic pattern being of rectangular Outline and having sixteen possiblestud position-s arranged in four columns and four rows, the rows beingparallel to one side of the rectangular Outline and the columns parallelto an adjacent side of the rectangular Outline; the points of attachmentof the studs to the tubes being located only as tollows: a first stud inthe first row, fourth column; a second .stud in the second row, thirdcolumn; a third stud in the third row, first column; and a *fourth studin the fourth row, second column; the axis of the studs of -a columnlying in an imaginary plane, said imaginary plane `being perpendicularto the longitudinal axis of the tubes and containing the column, theaxis of each stud being slanted out of a direction perpendicular to thelayer of refractory material, the first and third toward one end of thecolumn and the second and fourth toward the other end of the column.

4. The rfurnace lining of claim 3 wherein the tubes are of circularcross section, the first and second rows being on a single tube and thethird and fourth rows on an adjacent single tube.

5. In a furnace lining comprising rows of interconnected cooling tubes-arr anged in a single plane, studs projecting from said tubes towardthe interior of the furnace when the lining is in Operating position anda layer of refractory material enclosing said studs and located betweensaid tubes and the interior of said urnace, the improvement wherein saidstuds are long enough and so slanted from a plane at right angles to thelayer of refractory material and passing through the longitudinal axisof the tube from which the stud projects as to overlap studs projectingin the opposite slanting direction from an adjacent tube, when viewed ina plane at right angles to the longitudinal -axis of said tubes, to anextent so that the ends of overlapping studs project beyond each othernear ly to -a plane at right angles to the layer of refractory materialand passing through the longitudinal axis of an adjacent .tube.

6. In a furnace lining comprising rows of interconnected cooling tubes,studs projecting from said tubes toward the interior of the furnace whenthe lining -is in Operating position and a layer of refractory materialenclosing said studs and located between said studs and the interior ofsaid furnace, the improvement wherein said studs are long enough and soslanted from a plane at right angles to the layer of refractory materialand passing through the longitudinal axis of the tube from which thestud projects as to overlap studs projeoting in the opposite slantingdirection from an adjacent tube, when viewed in a plane at right anglesto the longitudinal axs of said tubes, to an extent so that the ends ofoverlapping studs project beyond each other and into the portions ofsaid layer of refractory material surrounding the overlapping studssufiiciently to lock said portions against sep-aration from the rest ofsaid layer of refractory material, and wherein said studs each have amaximum cross-section where joined to said tube and minimumcross-section at the outer end of said stud.

7. In a furrace cover comprising rows of interconnected cooling tubes,studs projecting from said tubes toward the interior of the furnace whenthe cover is in Operating position and a layer of refractory materialenclosing said studs and located between said tubes and the interior ofsaid furnace, :the improvement wherein said studs are 'long enough andso slanted from a plane at right angles to the layer of refractorymaterial and passing through the longitudinal axis of the tube fromwhich the stud projects as to overlap studs projecting in the oppositeslanting direction from an adjacent tube, when viewed in a plane atright angles to the longitudinal axis of said tube, to an extent so thatthe ends of overlapping studs project beyond each other and into theportions of said layer of refractory material surrounding theoverlapping studs sufliciently to lock said portions against separatonfrom the rest of said layer of refractory material.

References Cited in the file of this patent UNITED STATES PATENTS2,190,271 Powell Feb. 13, 1940 2,360,855 Dow et al Oct. 24, 19442,648,714 Williams et al Aug. 11, 1953 FOREIGN PATENTS 1,053,707 GermanyMar. 26, 1959 OTI-IER REFERENCES German application Serial No. =D16,444,printed December 27, 1956 (KL. 13a 8).

